Metalorganic chemical vapor deposition of (ba1-x Srx)RuO3 /Ba1-x Srx)TiO3 /(Ba1-x SRx)RuO3 capacitors for high dielectric materials

ABSTRACT

A dynamic random access memory device having a ferroelectric thin film perovskite (Ba 1-x  Sr x )TiO 3  layer sandwiched by top and bottom (Ba 1-x  Sr x )RuO 3  electrodes. The memory device is made by a MOCVD process including the steps of providing a semiconductor substrate, heating the substrate, exposing the substrate to precursors including at least Ru(C 5  H 5 ) 2 , thereafter exposing the substrate to precursors including at least TiO(C 2  H 5 ) 4  and thereafter exposing the substrate to precursors including at least Ru (C 5  H 5 ) 2 .

This is a divisional of application Ser. No. 08/501,352 filed on 12 Jul.1995, now U.S. Pat. No. 5,629,229.

FIELD OF INVENTION

The present invention relates to dynamic random access memory devices("DRAMs"), and more particularly to high capacitance capacitors forDRAMs and a method of making high capacitance capacitors for DRAMs.

BACKGROUND OF THE INVENTION

Semiconductor devices such as DRAMs have decreased in size and increasedin charge storage density dramatically over the last 20 years. As thecapacity of DRAM cells has increased and their size has decreased, thedesign of the cells has become increasingly complex in order to achievesufficient electrical capacitance to hold the electrical chargerepresenting the stored data.

Traditionally, silicon dioxide has been used as the dielectric in thecapacitors of DRAM cells. Silicon dioxide, however, has a relatively lowdielectric constant and thus, limited charge storage density. This hasresulted in experimentation with the use of materials with higherdielectric constant to increase the electrical capacitance in these verysmall complex cells.

In recent years ferroelectric materials such as barium strontiumtitanate (Ba_(1-x) Sr_(x) TiO₃)) have been examined for use in dynamicrandom access memory devices. Ba_(1-x) Sr_(x) TiO₃ films are desirablein that they have relatively high dielectric constants (ε_(r)), rangingfrom 300 to 800 depending on the value of "x". Ba_(1-x) Sr_(x) TiO₃films are easy to prepare and are structurally stable. Because of theirhigh dielectric constants, Ba_(1-x) Sr_(x) TiO₃ films provide almost anorder of magnitude higher capacitance density in DRAM cell capacitorsthan conventional dielectrics such as silicon dioxide. Further, Ba_(1-x)Sr_(x) TiO₃ has a low Curie point temperature, ranging between 105° K to430° K depending on the value of "x". This results in a smalltemperature coefficient of capacitance. Additionally, Ba_(1-x) Sr_(x)TiO₃ is not affected by piezoelectric effect because it exhibits aparaelectric phase at room temperature. This opens up the possibility ofintegrating a Ba_(1-x) Sr_(x) TiO₃ capacitor into the existing siliconand gallium arsenide ultra large scale integrated circuit (ULSI)technology to make a commercial dynamic random access memory device.

Several problems still need to be overcome, however, before acommercially viable memory product is available. Foremost among theseproblems is the degradation of ferroelectric devices due to fatigue, lowvoltage breakdown and aging. Degradation causes dielectric breakdown ofthe ferroelectric device and as such results in a decrease in thedielectric constant, thereby decreasing the charge density storagecapacity. A common cause of degradation is the interaction betweendefects in the materials and the ferroelectric-electrode interface/grainboundaries in the ferroelectric capacitor. For example, fatiguedegradation, which is one of the prime obstacles to forming high qualityferroelectric films, is caused by defect entrapment in theferroelectric-electrode interface.

Defect entrapment at the ferroelectric-electrode interface is caused byasymmetric ferroelectric-electrode interfaces and by non-uniform domaindistribution in the bulk. Asymmetric electrode-ferroelectric interfacesand/or non-uniform domain distribution in the bulk lead to asymmetricpolarization on alternating polarity. This results in an internal fielddifference which can cause effective one-directional movement of defectssuch as vacancies and mobile impurity ions. Because theelectrode-ferroelectric interface is chemically unstable, it providessites of lower potential energy relative to the bulk ferroelectric,thereby causing defect entrapment at the interface (see Yoo, et al.,"Fatigue Modeling of Lead Zirconate Titanate Thin Films", Jour. MaterialSci. and Engineering), resulting in a loss of dielectric constant in theferroelectric.

To overcome the problems associated with defects it is necessary tocontrol the defect concentration, defect migration to the interface, anddefect entrapment at the interface. Defect migration and entrapment canbe controlled by reducing the abrupt compositional gradient between theelectrode and the ferroelectric. It is also necessary to control thestate of the interface itself because lattice mismatch, poor adhesion,and large work function differences between the electrode and theferroelectric cause the interface to be chemically unstable.

The present invention is intended to overcome one or more of theproblems discussed above.

SUMMARY OF THE INVENTION

The present invention is a dynamic random access memory device having aferroelectric thin film perovskite layer sandwiched by top and bottomconducting oxide electrodes. The device in a preferred embodimentincludes a substrate of silicon, gallium arsenide or other knownsubstrate materials, a bottom electrode which is a thin film of(Ba_(1-x) Sr_(x))RuO₃, a ferroelectric thin film of (Ba_(1-x)Sr_(x))TiO₃ and a top electrode which is a thin film of (Ba_(1-x)Sr_(x))RuO₃.

The (Ba_(1-x) Sr_(x))TiO₃ ferroelectric of the present invention hasvery desirable properties for use in dynamic random access ferroelectricmemory devices, including ease of preparation, structural stability, alow Curie temperature at which the transition occurs from theferroelectric to the paraelectric state, a high saturation polarization,high dielectric constant, and relatively low piezoelectric coefficients.Additionally, (Ba_(1-x) Sr_(x))TiO₃ and (Ba_(1-x) Sr_(x))RuO₃ have avery similar crystal lattice structure which increases the stability ofthe ferroelectric-electrode interface and decreases the degradation ofthe ferroelectric device due to fatigue, low voltage breakdown andaging.

The (Ba_(1-x) Sr_(x))TiO₃ ferroelectric layer and the (Ba_(1-x) Sr_(x))RuO₃ conducting oxide electrode layers are applied to the substrate byutilizing either a three step metalorganic chemical vapor depositionprocess or by a liquid source delivery method. The three stepmetalorganic chemical vapor deposition (MOCVD) process for depositingthe (Ba_(1-x) Sr_(x))TiO₃ ferroelectric uses precursors of Ba(thd)₂ andSr(thd)₂, where thd=C₁₁ H₁₉ O₂, and Ti(OC₂ H₅)₄ with N₂ as a carrier gasand O₂ as a dilute gas. The MOCVD process for depositing the (Ba_(1-x)Sr_(x))RuO₃ conducting electrodes uses precursors of Ba(thd)₂ andSr(thd)₂, where thd=C₁₁ H₁₉ O₂, and Ru(C₅ H₅)₂ with N₂ as a carrier gasand O₂ as a dilute gas. The MOCVD process produces thin films withexcellent film uniformly, composition control, high density, highdeposition rates and excellent step coverage, utilizing fairly simpleequipment that is amenable to large scale processing.

The newer liquid source delivery method may also be used in applying the(Ba_(1-x) Sr_(x))TiO₃ ferroelectric layer and the (Ba_(1-x) Sr_(x))RuO₃conducting oxide electrode layers to the substrate, this method havingsome advantages over the MOCVD process previously described. MOCVDprecursor vapor delivery systems require the control of the temperatureand flow rate for each precursor. Some metalorganic precusors, such asSr and Ba, used in MOCVD of ferroelectrics are not stable at therequisite sublimation temperatures, making accurate control of the filmstoichiometry difficult over time. In contrast, the liquid sourcedelivery method dramatically simplifies the deposition process and alsosignificantly improves the process reproducibility.

In the liquid source delivery method, the metalorganic precursors aredissolved in an organic solvent or solvent mixture to form a precursorsolution, and injected into a vaporizer which is located upstream fromthe reactor inlet. The solvents for preparing the precursor solutioncould be one or a mixture of the following: aromatic hydrocarbon, cyclichydrocarbon and chain hydrocarbon.

The precursors could be one of the following: alkyls of elementscomprising Ba, Sr, Ru, or Ti; alkoxides of elements comprising Ba, Sr,Ru or Ti; β-diketonates of elements comprising Ba, Sr, Ru, or Ti;metallocenes of elements comprising Ba, Sr, Ru, or Ti; or a combinationof at least two alkyls, alkoxides, β-diketonates, and metallocenes ofelements comprising Ba, Sr, Ru, or Ti. The precursors could be dissolvedin solvents like tetrahydrofuran (C₄ H₈ O), because of its solvatingpower and its compatibility with the precursors at a molarity of 0.05 to0.5M. The precursor vapor will then be carried upstream by N₂ carriergas to the reactor inlet where deposition of the films takes place.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic depiction of a dynamic random access memory devicein accordance with the present invention.

FIG. 2 is a schematic diagram of a hot walled apparatus for use inapplying the (Ba_(1-x) Sr_(x))TiO₃ and (Ba_(1-x) Sr_(x))RuO₃ thin filmsin accordance with the hot-wall MOCVD process of the present invention.

FIG. 3 is a schematic diagram of a cold walled apparatus for use inapplying the (Ba_(1-x) Sr_(x))TiO₃ and (Ba_(1-x) Sr_(x))RuO₃ thin filmsin accordance with the cold-wall MOCVD process of the present invention.

FIG. 4 is a schematic diagram of a liquid source delivery system for usein applying the (Ba_(1-x) Sr_(x))TiO₃ and (Ba_(1-x) Sr_(x))RuO₃ thinfilms in accordance with the liquid source delivery method of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

A schematic depiction of a memory device 10 in accordance with thepresent invention is shown in FIG. 1. The device includes a substrate 20of a suitable material such as silicon, sapphire or gallium arsenide.The substrate 20 may be a multilayer structure having layers of siliconoxide, polysilicon or implanted silicon layers to form a complexintegrated circuit. A conductive oxide layer 22, acting as a bottomelectrode, is bonded to an upper surface 24 of the substrate 20. Aferroelectric conductive perovskite thin film 26 is bonded to theconductive layer 22 and another conductive oxide layer 28, acting as atop electrode, is bonded to the thin film 26. The top and bottomconductive oxide layers 28, 22 are thin films of (Ba_(1-x) Sr_(x))RuO₃and the ferroelectric perovskite layer 26 is a thin film of (Ba_(1-x)Sr_(x))TiO₃.

Deposition of the conductive oxide layers and the ferroelectric layer isa three step process. The first step is deposition of the thin layer 22of (Ba_(1-x) Sr_(x))RuO₃ onto a substrate 20 of a suitable material suchas silicon, sapphire or gallium arsenide, thereby forming the bottomelectrode. Thin film 22 is applied to the substrate 20 by eithermetalorganic chemical vapor deposition ("MOCVD") or liquid sourcedelivery method as described in greater detail below.

The second step of the three step process is deposition of thin film 26of the perovskite ferroelectric (Ba_(1-x) Sr_(x))TiO₃ by either MOCVD orliquid source delivery method as will be described.

The third step of the three step process is deposition of a second thinlayer 28 of (Ba_(1-x) Sr_(x))RuO₃ onto the (Ba_(1-x) Sr_(x))TiO₃ layer26 by either MOCVD or liquid source delivery method.

If the MOCVD process is used, there are basically process that can beused. The two MOCVD processes, hot wall MOCVD and cold wall MOCVD havebeen found to successfully deposit layers of the (Ba_(1-x) Sr_(x))RuO₃and (Ba_(1-x) Sr_(x)) TiO₃. FIG. 2 is a schematic diagram MOCVDapparatus 40. The hot wall MOCVD apparatus consists of first, second-andthird stainless steel bubblers 42, 44 and 46. N₂ cylinders 48 areconnected by inlet conduits 50 to the first, second and third stainlesssteel bubblers, 42, 44 and 46. A mass float controller 52 is in fluidcommunication with each inlet conduit 50 as is a fluid control valve 54.Outlet conduits 56 connect each stainless steel bubbler 42, 44 and 46 toa furnace delivery conduit 58. Fluid control valves 54 are provided inthe outlet conduits 56 for controlling the outflow of the first, secondand third stainless steel bubblers. Also connecting to the furnacedelivery conduit 58 downstream from the first, second and thirdstainless steel bubblers 42, 44 and 46 are an O₂ cylinder 60 and an N₂cylinder 62. Mass flow controllers 52 and values 54 are in fluidcommunication between the O₂ cylinder 60, the N₂ cylinder 62 and aconduit 64. A fluid control valve 54 on the furnace delivery conduit 58controls the flow of fluids from the first, second and third stainlesssteel bubblers 42, 44 and 46 into the reaction chamber 66.

A door 68 provides access for loading substrates 20 in the reactionchamber 66. A vacuum gauge 70 in fluid communication with the reactionchamber 68 is provided for monitoring the vacuum pressure in thereaction chamber 66. A three zone furnace 72 is provided for controllingthe deposition temperature in the reaction chamber 66. Alternatively, asubstrate heater could be employed. A furnace outlet conduit 74 isprovided for exhausting waste vapors from the reaction chamber 66. Aliquid N₂ cold trap 76 is provided on the furnace outlet conduit 74 forcapturing waste N₂ gas. A vacuum pump 78 provides the appropriatechamber pressure within the reaction chamber 66 and promotes exhaustingof waste gases from the reaction chamber 66. A fluid control valve 54 isprovided in the conduit 76 for controlling exhaust flow.

A bypass line 80 connects the furnace delivery conduit 58 downstream ofthe first, second and third stainless steel bubblers 42, 44 and 46 andupstream of the conduit 64 to the furnace outlet conduit 74 downstreamof the furnace outlet conduit fluid control valve 54. A fluid controlvalve 54 is provided on the bypass line 80 for controlling the flow offluid therethrough.

The warm temperature zone within the hot walled MOCVD apparatus 40 isindicated by dotted lines 82. Use of the hot walled MOCVD apparatus 40for depositing thin films of (Ba_(1-x) Sr_(x))RuO₃ requires introductionof the precursor materials Ru(C₅ H₅)₂, Sr(C₁₁ H₁₉ O₂)₂ and Ba(C₁₁ H₁₉O₂)₂ into the first, second and third stainless steel bubblers 42, 44and 46. Carrier gas N₂ is provided from the N₂ cylinders 48 through theinlet conduits 50 into the bubble chambers 42, 44 and 46. Followingreaction in the bubble chambers 42, 44 and 46 effluent from the bubblechambers flows through into the furnace delivery conduit 58. The O₂ andN₂ cylinders 60, 62 provide a source of dilution and carrier gas to thefurnace delivery conduit 58. The valves 54 located throughout the systemprovide for desired fluid flow control. Inside the reaction chamber 66,the precursors suspended in the N₂ carrier gas and combined with the O₂dilution gas deposit a thin layer of (Ba_(1-x) Sr_(x))RuO₃ upon thesubstrates 20.

The hot walled MOCVD apparatus 40 can be used for MOCVD deposition ofthe ferroelectric perovskite thin film of (Ba_(1-x) Sr_(x))TiO₃ bysubstituting Ru(C₅ H₅)₂ as the precursor in the first stainless steelbubbler 42. The MOCVD processing conditions for depositing (Ba_(1-x)Sr_(x))RuO₃ and (Ba_(1-x) Sr_(x))TiO₃ films are set forth in Table 1 andTable 2, respectively, below:

                  TABLE 1                                                         ______________________________________                                        Precursors                                                                           Ba(thd).sub.2 Sr(thd).sub.2                                                                              Ru(C.sub.2 H.sub.5).sub.2                   ______________________________________                                        Bubbler                                                                              230-250° C.                                                                          180-200° C.                                                                         140-170° C.                          Temp.                                                                         Carrier                                                                              N.sub.2, 20-40 sccm                                                                         N.sub.2, 20-40 sccm                                                                        N.sub.2, 5 sccm                             Gas                                                                           Dilute Gas                                                                           O.sub.2, 500-1000 sccm                                                 Deposition                                                                           550° C.                                                         Temp.                                                                         Chamber                                                                              2-10 torr                                                              Pressure                                                                      ______________________________________                                         (where thd = C.sub.11 H.sub.19 O.sub.2 and sccm = standard cubic              centimeter per minute)                                                   

                  TABLE 2                                                         ______________________________________                                        Precursors                                                                           Ba(thd).sub.2 Sr(thd).sub.2                                                                              Ti(OC.sub.2 H.sub.5).sub.4                  ______________________________________                                        Bubbler                                                                              230-250° C.                                                                          180-200° C.                                                                         80-100° C.                           Temp.                                                                         Carrier                                                                              N.sub.2, 20-40 sccm                                                                         N.sub.2, 20-40 sccm                                                                        N.sub.2, 1-5                                Gas                               sccm                                        Dilute Gas                                                                           O.sub.2, 500-1000 sccm                                                 Deposition                                                                           500° C.                                                         Temp.                                                                         Chamber                                                                              2-10 torr                                                              Pressure                                                                      ______________________________________                                         (where thd = C.sub.11 H.sub.19 O.sub.2 and sccm = standard cubic              centimeter per minute)                                                   

FIG. 3 is a schematic diagram of a cold walled MOCVD apparatus 90. Likeelements of the cold walled MOCVD apparatus 90 and the hot walled MOCVDapparatus 40 are indicated with identical reference numerals and willnot be separately described. As appreciated by those skilled in the art,the cold-wall MOCVD apparatus 90 differs from the hot-wall MOCVDapparatus 40 in that (1) only the substrates 20 are heated, (2) thesource vapors are vertically injected onto the substrate from thefurnace delivery conduit 58 and (3) the wall 92 of the reaction chamber66 (or the deposition temperature) is kept around 250° C. Otherwise, theconditions set forth in tables 1 and 2 are identical.

A substrate heater 94 is separated from the substrate 20 by a substrateholder 96. The substrate heater 94 can be operated at a maximumtemperature of 900° C. with the temperature of the substrate heaterbeing position insensitive within an 8° C. range and the variation intemperature with time being within 1° C.

The substrate holder 96, which is made of INCONEL, directly supports thesubstrates 20 and is in direct contact with the substrate heater 94. Athermocouple 98 mounted directly inside the center of the substrateholder 96 monitors the temperature of each substrate. The substrates areadhered to the substrate holder 96 by silver paste. The silver pasteimproves heat conduction and temperature uniformity of the specimens.

The distance between the inlet of the furnace delivery conduit 58 andthe substrates can be varied from 1.5 to 10 cm. As is readily apparent,the set up and the control of the bypass line and the bubbler heaters issimilar to those of the hot-wall apparatus 40. Ti(OC₂ H₅)₄ or Ru(C₅ H₅)₂are used within the first bubble chamber 42 depending upon whether alayer of (Ba_(1-x) Sr_(x))TiO₃ or (Ba_(1-x) Sr_(x))RuO₃ is beingdeposited. In the first and third steps, the deposition of the top andbottom (Ba_(1-x) Sr_(x))RuO₃ electrodes is controlled to yield very thinlayers 22, 28 of (Ba_(1-x) Sr_(x))RuO₃.

In the second step, the ferroelectric (Ba_(1-x) Sr_(x))TiO₃ film 26 isdeposited. The (Ba_(1-x) Sr_(x))TiO₃ ferroelectric layer 26 depositedunder the conditions set forth above has been found to have a low Curietemperature at which the transition from the ferroelectric to theparaelectric state occurs. In addition to this relatively low Curietemperature, the (Ba_(1-x) Sr_(x))TiO₃ layer exhibits other favorablecharacteristics for DRAM cell applications, including a desireablesaturation polarization and a very high dielectric constant. Theseproperties are consistent with fatigue-free, high retentivity,ferroelectric memories.

Alternatively, as previously mentioned, the liquid source deliverymethod may be used to create the capacitors of the present invention.FIG. 4 is a schematic diagram of a liquid source delivery system. Thesource materials of the desired thin film compound are mixedstoichiometrically and held in the liquid form in an Erlenmeyer flask110. The source is transferred to the flash vaporization chamber 102 bya Masterflex Economy drive 128 (basically a pump with a liquid flowmeter) through a series of tubes as shown in FIG. 3. A needle valve 104is inserted in the flow line to control the flow of the liquid and isconnected to the source end by silicone tubing 106 and the vaporizationchamber end by stainless steel tubing 108. The source is transferredfrom the flask 110 to the silicone tubing 106 through a glass rod. Thevaporization chamber 102 is sealed on the source end by a flange 114.The stainless steel tube 108 that provides the path for the liquidsource delivery is inserted into the vaporization chamber 102 through atight fit hole drilled into the flange 114. The other end of the chamber102 is connected to the pyrolysis chamber of the MOCVD reactor, thetemperature of which is controlled by a preheat chamber temperaturecontroller 132. The transport rate of the solution to the vaporizationchamber 102 is varied from 0.1 to 10 sccm, depending on the size of theMOCVD reactor. The vaporization chamber 102 is heated as a whole and thetemperature is controlled using a temperature controller 118. Apreheated carrier gas (N₂) is used to transport the vaporized sourcefrom the vaporization chamber 102 to the pyrolysis chamber. The flowrate of the carrier gas is controlled using a mass flow controller 130.The carrier gas is sent through a preheat chamber 120 to heat the gases.

Using this method, the metalorganic precursors, either solids orliquids, are placed in flask 110 where they are dissolved in an organicsolvent to form a precursor solution.

The organic solvent for preparing the precursor solution could be one ora mixture of the following: aromatic hydrocarbon, cyclic hydrocarbon,and chain hydrocarbon. For example, the solvents could be one or amixture of the following: tetrahydrofuran (C₄ H₈ O), isaopropanol (C₃ H₇OH), tetraglyme (C₁₀ H₂₂ O₅), xylene C₆ H₄ (CH₃)₂ !, toluene (C₆ H₅CH₃), and butyl acetate CH₃ CO₂ (CH₂)₃ CH₃ !. The precursors aredissolved in solvents like tetrahydrofuran (THF), because of theirsolvating power and their compatibility with the below mentionprecursors, at a molarity of 0.05 to 0.5M. The film composition will becontrolled by varying the molar ratio of each precursor in the solution.To lower the evaporation of the solution and to increase the stabilityof the precursors, additives like tetraglyme and isopropanol areutilized.

The precursors could be one of the following: alkyls of elementscomprising Ba, Sr, Ru, or Ti; alkoxides of elements comprising Ba, Sr,Ru or Ti; β-diketonates of elements comprising Ba, Sr, Ru, or Ti;metallocenes of elements comprising Ba, Sr, Ru, or Ti; or a combinationof at least two alkyls, alkoxides, β-diketonates, and metallocenes ofelements comprising Ba, Sr, Ru, or Ti.

Table 3 provides some examples:

                  TABLE 3                                                         ______________________________________                                        Element    Composition                                                        ______________________________________                                        Ba         Ba(thd).sub.2 or Ba(fod).sub.2                                     Sr         Sr(thd).sub.2 or Sr(fod).sub.2                                     Ru         Ru(C.sub.2 H.sub.5).sub.2                                          Ti         Ti ethoxide = Ti(C.sub.2 H.sub.5 O).sub.4 ; Ti propoxide =                    Ti(C.sub.2 H.sub.5 O).sub.4 or Ti(thd).sub.3                       ______________________________________                                         where thd = C.sub.11 H.sub.19 O.sub.2 and fod = C.sub.10 H.sub.10 F.sub.7     O.sub.2                                                                  

Either process described above provides a commercially viable memoryproduct by eliminating degradation of the ferroelectric device due tofatigue, low voltage breakdown and aging. These advantages stemprimarily from the similar crystal lattice structures of the (Ba_(1-x)Sr_(x))TiO₃ and the (Ba_(1-x) Sr_(x))RuO₃ which increases the stabilityof the ferroelectric-electrode interface. Application of the (Ba_(1-x)Sr_(x))TiO₃ and the (Ba_(1-x) Sr_(x))RuO₃ layers using the eitherprocess produces thin films with excellent film uniformity, compositioncontrol, high density, high deposition rates and excellent step coveragewhile utilizing fairly simple equipment that is amenable to large scaleprocesses.

What is claimed is:
 1. A capacitor comprising:top and bottom electrodesof (Ba_(1-x) Sr_(x))RuO₃ ; and a ferroelectric layer of (Ba_(1-x)Sr_(x))TiO₃ between the top and bottom electrodes.
 2. The capacitor ofclaim 1 in combination with a semi-conductor substrate, the bottomelectrode residing on the substrate.
 3. The capacitor of claim 1produced by a process of metalorganic chemical vapor deposition.
 4. Thecapacitor of claim 2 wherein the (Ba_(1-x) Sr_(x))RuO₃ layer isdeposited on the substrate by a process of metalorganic chemical vapordeposition which includes precursors of Ru(C₅ H₅)₂, Sr(C₁₁ H₁₉ O₂)₂ andBa(C₁₁ H₁₉ O₂)₂.
 5. The capacitor of claim 2 wherein the (Ba_(1-x)Sr_(x))TiO₃ layer is deposited by a process of metalorganic chemicalvapor deposition which includes precursors of Ti(O₂ H₅)₄, Sr(C₁₁ H₁₉O₂)₂ and B(C₁₁ H₁₉ O₂)₂.